Differences

This shows you the differences between two versions of the page.

--- opinion:frater_secessus:troubleshooting [2024/12/10 16:47]
frater_secessus [is it repeatable and predictable?]
+++ opinion:frater_secessus:troubleshooting [2024/12/10 17:24] (current)
frater_secessus [narrowing it down]
@@ Line 102: / Line 102: @@
-==== where does it start? ====
+==== narrowing it down ====
+We've come this far in the process and **this is our first attempt at doing what most people think of as troubleshooting** (testing with [[:#multimeters|a multimeter]]).
+=== measuring voltage ===
+Measuring voltage with a 'meter is fundamental to troubleshooting in a van.  Let's assume a lava lamp plugged into your 120vac circuit no longer works.  Anything between (and including) the battery and lava lamp could be causing the issue.
+There are many points to test
+  -  the 12v battery bank voltage at the terminals
+  -  the 12v input terminals on the inverter
+    - the 120vac output terminals on the inverter
+  -  120vac outlet where the lamp is plugged in (assuming it's not directly plugged into the inverter)
+In practice we usually don't need to test them all.  We can make some fair assumptions on our preliminary investigation:
+  * if voltage at the battery is low (lead) or ~zero (lithium) the battery needs to be charged. If voltage is normal the problem probably lies elsewhere.
+  * if other things are running off the inverter right now then the problem is unlikely to be the inverter itself.  Note, however, that it's possible that the lava lamp pushes the inverter over its limits.
+  * if nothing is running off the inverter and there are not lights on it then a fuse may have popped. 0v at the inverter inputs will help confirm this.
+  * if the lava lamp doesn't run when connected to a normal shore power outlet at Starbucks then the problem is probably the lamp.
+If things still don't make sense we might have to explicitly test those assumptions.  Or test at each point.
+  * if the battery terminal voltage sags under load the battery is undersized and/or unhealthy
+  * if battery voltage is ok but low at the inverter terminals then the [[electrical:12v:voltage_sag|voltage sag]] is likely caused by resistance.  Bad connections, undersized wiring, etc.
+On wiring runs that do not have observable loads on them we might have to take a voltage reading at each one.  If there are many connections you might start at the midpoint to rule out 50% of the possibilities, repeating until you find the offender or exhaust the possibilities.
+Note:  on circuits presently carrying power voltage testing is also indirectly continuity testing (see below).  If there is voltage there //must// be continuity between the test points.
+=== measuring current ===
+Sometimes voltage doesn't tell us what we need to know.  Finding a parasitic load is often done by watching current going out of the battery and pulling fuses one at a time or otherwise breaking the subcircuits.  When the offending circuit is taken offline the current will drop by that amount.
+Current measurements are also important for understanding how your system is functioning:  how much charge you're getting, etc.
+If you have [[electrical:12v:battery_monitor|a battery monitor]] installed you can watch the net charge/discharge that way.   Or you can use a clamp meter (see below).  Or for small currents you can break the circuit and use the meter inline reveal the current.    The clamp meter is the fastest, easiest way to measure current on a particular wire.
+=== measuring continuity ===
+Meters can measure continuity.  This might be useful for testing a fuse in the hand;  it might look good but actually be popped.
+=== measuring resistance ===
+Meters can also measure resistance but that is beyond the scope of this simple guide.
+=== testing components ===
+==== tools ====
-We've come this far in the process and **this is our first attempt at doing what most people think of as troubleshooting** (testing with a multimeter).
 === multimeters ===

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools